1. Field of the Invention
The present invention relates to an adaptor device for a car radio connected to and for use in a vehicle-mounted car radio.
2. Description of the Related Art
There has hitherto been known an vehicle-mounted system in which an FM transmitter is connected to an audio reproducing player or the like and a radio wave transmitted from the FM transmitter is received by a car radio (for example, refer to Japanese Patent Laid-Open No. 6-309854). In this vehicle-mounted system, a vehicle-mounted antenna is used for the car radio to receive the radio wave.
In the above described vehicle-mounted system, however, a radio wave transmitted from the FM transmitter installed within the vehicle room is received by use of the vehicle-mounted antenna provided outside the vehicle body, so the receiving state deteriorates, thus causing a problem. In Japanese Patent Laid-Open No. 6-309854, there is a description such that since the FM transmitter and the vehicle-mounted antenna are very close to each other, reception can be performed by use of the vehicle-mounted antenna without trouble. However, the vehicle body is largely made of metal. In addition, a patterned conductor of heater for defrosting is often attached to the rear window. Thus a radio wave transmitted from the FM transmitter installed within the vehicle room hardly reaches the vehicle-mounted antenna disposed in the vicinity of the trunk or the like. Consequently, when the transmission level of a radio wave transmitted from the FM transmitter is low, satisfactory reception is difficult to achieve via the vehicle-mounted antenna.